With the ongoing worldwide AIDS epidemic, scientists are continually searching for immune correlates of protection in order to design an effective HIV vaccine. Given the difficulty in generating broadly neutralizing antibodies against HIV, researchers have turned to vaccines that specifically target cytolytic CD8+ T-cell populations since these cells are important for control of viremia during acute and chronic HIV infection. Recent studies have shown that development and maintenance of HIV-specific CD8+ T-cell cytolytic effector function is a key factor in long-term control of HIV disease progression. While much is known about CD8+ T- cell differentiation and function, little is known about the mechanisms controlling the acquisition of the cytolytic functions necessary to clear chronic infections in humans. The transcription factors, Tbx21/T-bet and Tbr2/Eomes, have been implicated as critical regulators of CD8+ T-cell effector differentiation, including transcriptiona regulation of effector functions, such as perforin, granzymeB and interferon-? in mice. Preliminary data in our laboratory suggest that T-bet is linked to higher expression of the cytolytic effector genes, perforin and granzymeB, in HIV-specific CD8+ T-cells from HIV elite controllers; however, little is known about the actual downstream targets of T-bet or Eomes in human CD8+ T-cells. Additionally, the mechanism(s) for how T-bet and Eomes expression and function are regulated in CD8+ T-cells is unclear. Type I IFN (IFN?) has been implicated in the enhancement of effector function, including upregulation of perforin, IFN?, T-bet, Eomes and other cytolytic genes in both human and mice. Furthermore, IFN??treatment of HIV+ individuals has been linked to decreases in viremia and increases in HIV-specific CD8+ T-cell cytolytic potential suggesting it may be an attractive adjuvant for future HIV vaccines. Here, we seek to better understand both the regulation of T-bet and Eomes by IFN? and the role these factors play in controlling effector programming in human CD8+ T-cells in order to better understand the functional nature of protective CD8+ T-cell responses in HIV infection. To this end, we will perform chromatin immunoprecipitation in activated primary human CD8+ T-cells in the presence and absence of IFN?, followed by high-throughput Illumina sequencing analysis to identify novel effector gene targets. Additionally, we will determine the cytolytic effects of IFN? on HIV-specific CD8+ T-cells, as well as, define the role of IFN? on T-bet, Eomes and novel effector target genes expression and function. Overall, we aim to gain new insights into the mechanisms through which IFN? modulates T-bet, Eomes, and their downstream targets during CD8+ T-cell differentiation in hopes that our findings might provide novel mechanisms through which cytolytic CD8+ responses can be elicited through the use of vaccines during chronic infections. PUBLIC HEALTH RELEVANCE: Since cytolytic CD8+ T-cells are attractive targets for HIV vaccine development but the molecular requirements involved in the regulation and generation of effector CD8+ functions in humans is not well defined, we are proposing to characterize the effects of the inflammatory cytokine, Type I IFN, on the expression and function of T-bet and Eomes, key transcription factors involved in the acquisition of effector function. We will identify novel downstream effector gene targets of T-bet and Eomes that are upregulated in response to IFN treatment and we will extend these studies to look directly at the roles of IFN?, these transcription factors, and their downstream targets in driving cytolytic activity in HIV-specific CD8+ T-cells from HIV+ chronic progressors. Together these studies will provide key information necessary to better understand correlates of protection against HIV as well as determine the effectiveness of IFN? as a possible adjuvant in future HIV vaccines.